A general problem in printers, and especially in large format printers, is controlling the paper expansion that occurs when a lot of ink is placed on some media (especially on low cost paper based media). Under certain circumstances, this expansion ends up creating bubbles in the print medium that make the printheads crash against the media (damaging the plot and eventually the print heads).
In existing printers, the pinch wheels continuously engage the print media at the same locations in the direction of the scan axis, i.e. the direction in which the printhead moves during each printing pass. Thus the pinch wheels prevent the paper from expanding laterally, i.e. in the direction of the scan axis, to avoid the formation of the bubbles mentioned above. Accordingly, unwanted concentrations of ink are formed on the medium, which leads to a deterioration in print quality.
The present invention seeks to overcome or reduce the above problem.